The present invention relates to semiconductor fabrication and, more particularly, to an afferent polishing media for chemical mechanical planarization (xe2x80x9cCMPxe2x80x9d).
In the fabrication of semiconductor devices, CMP is used to planarize globally the surface of an entire semiconductor wafer. CMP is often used to planarize dielectric layers as well as metallization layers. As is well known to those skilled in the art, in a CMP operation a wafer is rotated under pressure against a polishing pad in the presence of a slurry.
During a CMP operation, the film removal process is typically controlled by either timing the operation or using a variety of endpoint techniques to determine the end of the process-cycle. These control techniques are typically deployed with the wafer pressed face down into a polishing pad and thereby obscuring the majority of the wafer surface from viewing using conventional methods. Thus, one drawback of the control techniques currently used in CMP operations is that they fail to provide sufficient spatial recognition of both wafer-level and die-level topography changes. This leads to poor within-wafer (WIW) film removal process control.
In view of the foregoing, there is a need for a polishing media that provides enhanced spatial insight to die-level and wafer-level planarization characteristics in real time and thereby enables active WIW film removal process control during a CMP operation.
Broadly speaking, the present invention fills this need by providing an afferentbased polishing media for chemical mechanical planarization (CMP) that includes sensors for providing information regarding the process evolution across the wafer substrate during the CMP operation. As used herein, the term xe2x80x9cafferent-basedxe2x80x9d is meant to generally define the process by which impulses are conducted from the periphery of the pad media body (e.g., asperities) to a central control, such as a computer control station.
In accordance with one aspect of the present invention, a first polishing media for CMP is provided. This polishing media includes an underlayer and a plurality of pressure sensors provided on the underlayer. At least some of the pressure sensors have a pad asperity provided thereon. In one embodiment, the pressure sensors are micro electromechanical systems (MEMS) pressure transducers. In another embodiment, the pressure sensors are MEMS thermal actuators that monitor at least one of localized strain and temperature variation.
In one embodiment, the pad asperities are comprised of one of a urethane-based material, an engineered plastic material, a ceramic material, and magnetic fluids. These materials, and other well know in the manufacture of MEMS can be used to provide localized asperity bulk-property control. In one embodiment, the polishing media includes wiring for providing sensory communication to a system control. In one embodiment, the underlayer is formed in discrete sections.
In accordance with another aspect of the present invention, a second polishing media for CMP is provided. This polishing media includes an underlayer having a plurality of pad asperities and a plurality of chemical sensors affixed to the underlayer. In one embodiment, the chemical sensors are embedded in the underlayer. In one embodiment, at least some of the chemical sensors are configured to detect metal ions selected from the group consisting of Cu, Ta, Ti, Al, W, and Pb. In one embodiment, at least some of the chemical sensors are configured to detect organic species. In one embodiment, at least some of the chemical sensors are configured to detect inorganic species.
In accordance with a further aspect of the present invention, a third polishing media for CMP is provided. This polishing media includes an underlayer. A plurality of pressure sensors are provided on the underlayer, with at least some of the pressure sensors having a pad asperity provided thereon. A plurality of chemical sensors and a plurality of piezoelectric elements also are provided on the underlayer. Each of the piezoelectric elements is coupled to at least one of an adjacent pressure sensor and an adjacent chemical sensor.
In one embodiment, at least some of the piezoelectric elements provide localized pressure in either a static or dynamic mode. In one embodiment, at least some of the piezoelectric elements induce localized electric fields to increase chemical dissolution rates and or change the hardness of the pad-asperity in contact with the wafer substrate. In one embodiment, at least some of the piezoelectric elements induce localized heating/cooling elements to change the chemical reactivity of the slurry chemistry and or change the hardness of the pad-asperity. In one embodiment, at least some of the piezoelectric elements have a pad asperity provided thereon.
It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention, as claimed.